140 UNTENABLE NOTIOIT. 



these subjects. In the various publications 

 relating to the progress of that singular dis- 

 ease in potatoes that committed such ravages in 

 the autumn of 1845, remarks were made upon 

 fungi, which showed that the authors of them 

 had made no accurate observations with re- 

 gard to the real characteristics of these singu- 

 lar pests. Every well-informed botanist at 

 once detected these mistakes, and perceived 

 that no practical advantage could be derived 

 from the advice offered on such erroneous 

 foundations. It has been already stated, that 

 no good reason can be given for their constant 

 appearance under certain circumstances, but 

 the almost universal diffusion of their sporules, 

 whose minuteness renders them capable of 

 abounding in almost every situation. The 

 difficulty is to conceive, floating, as they do, 

 unseen in the atmosphere, how any place can 

 be free from their presence. Nevertheless 

 there have been speculators who, having 

 marked their constant appearance on the same 

 places of growth under similar circumstances, 

 have ventured to conceive that they are the 

 results of what is called spontaneous genera- 

 tion. Such persons think that certain condi- 

 tions of matter give rise to vitality of the low 



